Shadowsphere

The Shadowsphere is an artifact in Heretic. It looks like an ethereal green sphere with a face. Activating the Shadowsphere gives the player the Heretic ghost attribute for 60 seconds, becoming translucent and gaining immunity to non-magical attacks (such as the Firemace's attacks). It also decreases the likelihood of idle monsters noticing the player, and causes their aim to become erratic.

This item is included in the items percentage displayed at the end of each level.

Strategies

 * The Shadowsphere will make the player invulnerable to the axes thrown by Undead warriors, so it is particularly useful when facing them. Note that the Undead warrior's melee axe will still cause damage.
 * Iron liches are also good enemies to use a Shadowsphere against. It prevents their tornado attacks from homing in and also grants a little extra protection from direct hits by the ice clusterbombs.

Appearance statistics
In the IWADs the shadowsphere is first encountered on these maps per skill level:

The IWADs contain the following numbers of shadowspheres per skill level:

Bugs
Due to a bug involving an out-of-bounds array read, firemace spawn spots on the unnamed E4M1 in the first v1.0 release of the registered Heretic will spawn shadowspheres at any spot where a firemace did not randomly spawn. This is caused by reading the first entry of one of the game's internal ambient sound sequences, which happens to have the value "5", as if though it were an enumeration value. All other episodes spawn deliberately chosen enemies, not power-up items, when executing this routine. This behavior was removed from later versions of the game.

Other games
Hexen II has a similar item called "Invisibility Sphere".